Tech prob - tail & instrument lights dimming/blinking

My hubby is trying to get my XT250 passed for rego, they've knocked us back for one thing & thats the brake/tail & instrument lights dimming each time as the indicators turn on. Anyone have any ideas?

So far we've checked all the wiring to make sure all the connections were/are clean & secure, all the way from the battery to each light bulb. We've heard that poor earthing could also cause the same problem, each bulb has been metered to make sure each ground is actually ground, they tested ok, so we grounded each of these to make sure anyway. We used the tail light to test, so by disconnecting different things (at the plugs) we ruled out the dash lights & head light. By disconnecting the key switch plug & linking the 6V power rail at the plug we ruled this out too, & doing the same for the indicator/dimmer switch assembly we ruled out any poor connections. With ALL but the necessary disconnected, the tail light still dims when the indicator flashes.

We decided to try & rule out the bike's wiring all together by crudely wiring up two 6V 17W globes from the indicators straight to the battery (with all but the necessary disconnected) & manually turning on & off the 2 indicator lights by hand (while the bike was running & not running) we could see the tail light still dimming.

Using the voltmeter we measured the new battery while the bike was running & it measured about 7.5VDC, while not running it measured 6.2V.

My hubby is thinking that the 6V system seems to just do it, is this normal?

Thanks to any answerers in advance

p.s I'm not the technical one, hubby is, he'll be the one implementing any answers!

I had a DT175 from 1984 with a 6volt system and I used to have this problem, a new battery helps but it still used to dim the tail light when the blinkers were on, the older the battery, the worse it got.

Never worried me much though.

I would still suspect either a crook earth, or a bad contact in a lamp socket. Being a 6 volt system, all contact surfaces need to be A1.

HTH.

Yep, crook/rusty earth. Take all your bulbs out and give their bases and the sockets a going over with very very fine wet and dry.

If that doesn't fix it pull the lights out and check the cabling going into them. You may have corroded terminals inside the terminal blocks. Clean these as well with wet and dry and squirt WD40 into everywhere.

Mick

Thanx for the quick replies guys, we appreciate it

We checked out everyones answers today, & hubby said that unfortunately he has tried all of the above suggestions already, he was working on the bike all day yesterday, & tried the above (amongst other things), but still no go! Hes taken the bike to two different mechanics, & both reckon that its a ground/earth problem, but hubby highly disagrees & thinks its something else, seeing as hes seemed to have proved (by testing everything) that its not a ground problem, but we just dont have any more ideas on what it could be, its VERY perplexing!

The annoying thing is, they won't pass the bike for the blueslip until this problem is fixed, & its proving to be a real doosy - i just got my L's about 4 weeks ago & i STILL haven't been able to ride yet cos of this problem (& the bike pulled apart in the garage!), i am sooo tempted to just ride it unregistered on the road, but i wont risk it, so am HOPING that someone has some more suggestions that we can try! Thanx again, i have my fingers crossed!

Make sure you have all the right globes too.
You'll need to check electrical specs as someone in the past may have puyt higher rated bulbs in

I'm no expert in lectrics, but have a couple of thoughts....

I'm not sure if it makes any difference, but what polarity is the rear tail light bulb? Does it still dim if the wires are the otehr way round?

What condition is the indicator relay in? If the relay is drawing too much current, it may steal current from the next circuit?

Have you tried connecting the tail light negative direct to earth rather than the wiring lume?

I'm no expert in lectrics, but have a couple of thoughts....

I'm not sure if it makes any difference, but what polarity is the rear tail light bulb? Does it still dim if the wires are the otehr way round?

What condition is the indicator relay in? If the relay is drawing too much current, it may steal current from the next circuit?

Have you tried connecting the tail light negative direct to earth rather than the wiring lume?

No polarity on a bulb Mike

I'm no expert in lectrics, but have a couple of thoughts....

I'm not sure if it makes any difference, but what polarity is the rear tail light bulb? Does it still dim if the wires are the otehr way round?

What condition is the indicator relay in? If the relay is drawing too much current, it may steal current from the next circuit?

Have you tried connecting the tail light negative direct to earth rather than the wiring lume?

No polarity on a bulb Mike

I didn't think there was, but thought it worth a check anyway.

Have you tried lower-wattage bulbs?

The 6V is a bit of a bugger, not sure there's still much around. I was going to suggest a LED Flasher unit and LED bulbs...but I guess you're screwed there.

One thing that just struck me is the idle speed - is it too low and hence you're not putting out the full amount of amps from your regulator? Does it do the same thing with the idle turned up slightly?

...still think it's an earth .

Mick

Hi guys, we're back, here is a direct quote from the hubby:

the idle is set to ~1200rpm, if idle is lower it doesnt dim any further, the workshop manual reckons that it should pump out ~1-1.6A @ 2500rpm, the lights do increase a little in brightness when the idle is turned up to ~2500rpm but ive heard thats normal. i am thinkin strongly about the LED flasher unit & bulbs, i found a website that caters for the flasher & tail light but not the indicators (www.classicandvintagebulbs.com), still lookin for that. It just seems strange that i have to modify it to pass rego!? But if thats what it takes then i guess i have to.

& he also said this:

if the 2 bulbs are ran separately (outside of the bikes wiring harness) & connect another 6V bulb they all dim, to allow for sharing of the current from the battery, i double checked this against a beefy bench power supply & the same thing occured.

We'd like to know if anyone on the forum has a 6V battery system where it doesnt dim, if thats the case, what wattage bulbs are you using in the indicators & what is the capacity of your battery? The battery we have is a 6N6-3B1 (which is 6V 6Ah) & bulbs are 6V 17W, 2 bulbs draws 5.6A, near if not the maximum capacity of the fully charged battery.

Thanks so much again everyone, all advice is appreciated

Yep it's no wonder the other lights are dimming. What type of bulb are they, do you have a pic of them including the base?

I found these in five mins: http://www.jaycar.com.au/productView.asp?ID=ZD0300&keywords=6v+bulb&form=KEYWORD

They're probably not going to fit, I imagine yours will be either a festoon type with a terminal at each end, or a bayonet type with either one or two terminals on the base (and possibly offset mounting pins).

I seem to remember a small DIY kit to convert an interior light in a car with a festoon type bulb to a high-intensity LED unit. A bit of tinkering would allow this to be used on a 6V system.

Here's one for 12V already made: http://www.jaycar.com.au/productView.asp?ID=ZD0484&keywords=festoon&form=KEYWORD

thks, Mick

This might be a bit daft, but if you replace the brake/tail light with an LED unit (I get mine from the ledshop.com.au, I think) then they won't dim. Not solving the problem so much as avoiding it. But they only supply 12 and 24V bulbs. Hmmm. So, if my HSC physics is reliable after 25 years, V=IR, which is the problem with most LED indicators. Not enough resistance to slow the flasher. But would a higher voltage indicator work, slowing the flasher but not dimming the lights?

I'm in Melbourne - is there anyone in NSW who could lend a couple of LED bulbs for a while?

I'm in Melbourne - is there anyone in NSW who could lend a couple of LED bulbs for a while?

That's why I asked what they looked like, I have a couple of eBAY LED Tail-lights I bought for the Honda that I know work on 12v that I didn't like the look of once they were in (not quite bright enough).

I can stick them in a padded envelope and send them up...

thks, Mick

Just wire the indicators to a "hidden" 6v Lantern battery to get you thru the roadworthy check

OR replace the battery with a 6Volt 12AH battery (Jaycar CAT. NO. SB2497)